1. Field of the Invention
The present invention relates to a motor structure and a method for manufacturing the same. Particularly, the invention is concerned with a motor structure and a method for manufacturing the same which motor structure and method permit easy insulation of stator poles formed by lamination of soft magnetic plates and easy mounting of components to the stator poles.
2. Description of the Prior Art
Small-sized synchronous motors and stepping motors are used as drive sources of various electronic devices such as floppy disk drives which are peripheral devices of personal computers. As an example of these motors there is known an inner rotor type motor in which a cylindrical rotor comprising poles of permanent magnets is disposed rotatably, and magnetic poles of a stator for generating a rotating magnetic field and thereby imparting a driving force to the rotor are disposed around the rotor in a face-to-face relation to the rotor. The stator poles are fixed to a substrate constituted by an insulated metal plate, while the rotor is supported by two bearings which are fixed respectively to the substrate and the stator poles. Onto the substrate are further fixed an electronic circuit for driving the motor, as well as components such as a position detecting coil for detecting the position of the rotor.
There also is known an outer rotor type motor in which a plurality of magnetic poles are projected radially from an annular yoke member and stator coils are wound round those magnetic poles to constitute stator poles, which stator poles are fixed to a substrate, while a shallow dish-like, or tray-like, rotary disk is disposed rotatably around the stator poles, and permanent magnets disposed inside the edge of the rotary disk are made face to face with the front ends of the stator poles.
According to the prior art, in fabricating the stator poles, no matter which type of motor may be concerned, a plurality of plates formed by pressing from a soft iron plates are stacked together to constitute a lamination stack, then for ensuring insulation between the lamination stack and a coil wound round the stack, an insulator is formed separately using an insulating material such as resin for example and is inserted into the coil winding portion of the lamination stack, or an insulating paint is sprayed directly to the lamination stack to form a thin insulating film on the whole surface of the lamination stack, or the lamination stack is subjected to a chemical treatment to form an insulating film on the surface thereof.
As mentioned above, the conventional assembling method involving separately forming an insulator for the lamination stack, inserting it between magnetic poles and winding a coil thereon, is expensive because of separate formation of the insulator and requires additional number of steps for assembling the insulator.
In the above formation of the insulating film by spray coating, it is impossible to form an insulating film having a uniform thickness throughout the whole surface of the lamination stack. Particularly, corners and edges are apt to be insufficient in thickness, which may cause dielectric breakdown during use of the motor. Further, in the recent assembling work for a smallsized motor, there is no space for clamping the whole of a pressed plate with pressure using eyelet or the like, with no clamping pressure exerted on the front-end peripheral edge of a stator pole tooth 100, as shown in FIGS. 6 and 7. Consequently, there occurs a gap between adjacent laminated plates of the assembled motor, and the plates are rusted in their interiors when used over a long years. Besides, when the stator is excited or the rotor is rotated, the plates vibrate and generate noise. There is an additional inconvenience such that bearing parts and other motor constituting parts must be mounted one by one to the substrate at the time of assembly. In FIGS. 6 and 7, the numeral 101 denotes a lamination stack which represents the whole of a stator pole, numeral 102 denotes a yoke portion, numeral 103 denotes a caulking portion for clamping plates 104, and numeral 105 denotes a coating surface which coats the lamination stack 101 in the spray method.
The present invention intends to eliminate the above-mentioned inconveniences of the prior art and it is an object of the invention to provide a novel motor structure and method for manufacturing the same which, when laminating plates as constituents of a lamination stack, can clamp the plates hermetically under pressure and can mount components of the motor to the lamination stack before mounting the motor to a substrate or the like.
According to the present invention, in order to achieve the above-mentioned object, there is provided a motor structure having a laminated structure of plural plates and also having a stator pole assembly formed with a component mounting portion, the motor structure comprising a synthetic resin layer which encloses and coats the plural plates in a closely contacted state of the plates, an overhang portion integral with the synthetic resin layer and which serves to not only hold but also position motor components, and an insulating film which covers a portion not coated with the synthetic resin layer. There also is provided a method for manufacturing a motor structure having a laminated structure of plural plates and a stator pole assembly formed with a component mounting portion, characterized in that a synthetic resin layer is formed on the surface of a lamination stack under the application of pressure from both upper and lower surfaces of the laminated plates which constitute the stator pole assembly.